This invention relates to physical exercise apparatus and more particularly to such apparatus as provides a variable resistance to the user.
Apparatus of the present type is generally known but it has not taken into account the different needs of the various parts of the population.
The needs of the physically handicapped or the patient involved in rehabilitative medicine while similar vary enormously from the needs of the professional athlete; the needs of the young adult vary from those of the older adult; and the needs for exercising of legs vary from those for exercising the arms or upper body.
It is generally agreed that the best muscle development may be best accomplished by maximum effort during exercise.
Exercise machines or apparatus should reflect this premise so that the resistance varies according to the muscle set being exercised. For example, in the upper body the load to movement should increase according to the extension of the muscle. However, due to the structure of the leg, apparatus for exercising the leg should reflect the fact that in extending the leg the force capable of being exerted moves from a maximum through a minimum and then increases again. The provision of straight variable resistance in leg exercising can do considerable damage to the leg and the provision of a constant resistance is desirable for maximum benefit.
Various types of commonly termed variable resistance machines have been provided in the prior art. Some of these machines such as exemplified by U.S. Pat. No. 3,708,166 employ pulleys; others such as U.S. Pat. No. 3,905,599 employ levers; and others such as U.S. Pat. No. 3,638,941 employ springs. Pulley and spring mechanisms are more expensive to produce and less reliable in performance. They are also difficult to control from the viewpoint of the user in that the variance in resistance is not as predictable.
More importantly, however, with lever actuated mechanisms such as that described in U.S. Pat. No. 3,905,599 the ratio of the initial lifting weight to the actual stack weight is always greater than 1.
This fact gives rise to two problems: the first is economic in that a greater number of weight blocks have to provide for the initial lift in lever operated mechanisms; and secondly, the heavy initial weight lift frequently makes the equipment unsuitable for rehabilitative applications and for young adults.